Transmission apparatus, transmitting method, reception apparatus, and reception method

ABSTRACT

In a broadcast scheme of transportation in an IP scheme, clock synchronization and presentation synchronization are well implemented. A clock synchronizing with time information acquired from an outside is generated. Time information including frequency information of the clock and synchronizing with the time information acquired from the outside is generated. A broadcast signal including transmission media, time acquisition information for acquiring decoding time and presentation time for every presentation unit of the transmission media obtained based on the generated time information, and the generated time information is transmitted.

TECHNICAL FIELD

The present technology relates to a transmission apparatus, atransmitting method, a reception apparatus, and a reception method, andmore particularly, to a transmission apparatus transmitting an IP-schemebroadcast signal including transmission media such as a video and anaudio, and the like.

BACKGROUND ART

As a next-generation broadcast scheme, transport schemes such as MMT ofperforming transportation in a content format based on an MP4 ISO BaseMedia File Format based on an IP protocol have been studied (refer to,for example, Non-Patent Document 1). By the MP4 ISO Base Media FileFormat, in order to obtain PTS/DTS in picture unit supplied by MPEG2Systems in the related art, time information corresponding to metadatacalled a moof box can be transported.

In this case, in order to perform efficient transportation, it isrequired to collectively transport metadata of encoded data in GOP unit.In this case, in a transmission side or a reception side, it isnecessary to have delay corresponding to the GOP, and the entire delayamount is increased by the amount corresponding to the GOP, so thatrequirements of low delay is not satisfied. In addition, since themetadata are determined by the amount corresponding to the GOP,influence by packet loss is increased.

CITATION LIST Non-Patent Document

-   Non-Patent Document 1: Study of ISO/IEC CD 23008-1 MPEG Media    Transport, [online], [search data: May 7, 2013], Internet <URL:    http://mpeg.chiariglione.org/standards/mpeg-h/mpeg-media-transport>

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present technology is to well implement clock synchronization andpresentation synchronization in a broadcast scheme of performingtransportation in an IP scheme.

Solutions to Problems

According to a concept of the present technology, there is provided atransmission apparatus including: a clock generation unit whichgenerates a clock synchronizing with time information acquired from anoutside: a time information generation unit which generates timeinformation including frequency information of the clock generated bythe clock generation unit and synchronizing with the time informationacquired from the outside: and a transmission unit which transmits abroadcast signal including transmission media, time acquisitioninformation for acquiring decoding time and presentation time for everypresentation unit of the transmission media obtained based on the timeinformation generated by the time information generation unit, and thetime information generated by the time information generation unit.

In the present technology, the clock synchronizing with the timeinformation acquired from the outside is generated by the clockgeneration unit. For example, the time information is acquired in an NIPlong format from an NIP server or another apparatus according to IEEE1588 PTP by the network time protocol (NTP).

Time information including frequency information of the clock generatedby the clock generation unit and synchronizing with the time informationacquired from the outside is generated by the time informationgeneration unit. For example, the frequency of the clock generated bythe clock generation unit may be configured so as to be 2**n. Hz.Therefore, the time information corresponding to the NTP long format canbe generated by the time information generation unit.

The broadcast signal including the transmission media, the timeinformation for acquiring the decoding time and the presentation timefor every presentation unit of the transmission media obtained based onthe time information generated by the time information generation unit,and the time information generated by the time information generationunit is transmitted by the transmission unit.

For example, the time acquisition information may include, for everypresentation unit group including a predetermined number of thepresentation units of the transmission media, presentation time of thefirst presentation unit of the presentation unit group and durationinformation for calculating the decoding time and the presentation timeof each presentation unit of the presentation unit group by referring tothe presentation time of the first presentation unit.

For example, the duration information may include decoding timeinformation of the presentation unit which is indicated by an offsetduration from the presentation time of the first presentation unit andis firstly transported, information indicating the duration of eachpresentation unit, and presentation time information which is indicatedby an offset duration from the decoding time of each presentation unit.In this case, in a case where the duration of each presentation unit isfixed, the number of bits necessary for transmitting the durationinformation can be suppressed.

In addition, for example, the duration information may include decodingtime information which is indicated by an offset duration from thepresentation time of the first presentation unit and presentation timeinformation which is indicated by an offset duration from the decodingtime for each of the presentation units. In this case, each decodingtime of each presentation unit can be obtained by adding the decodingtime information indicated by the offset duration to the presentationtime of the first presentation unit, so that the calculation process issimplified.

In addition, for example the duration information may include decodingtime information of the presentation unit which is indicated by anoffset duration from the presentation time of the first presentationunit and is firstly transported, decoding time information which isindicated by an offset duration from the decoding time of thepresentation unit before each of the second and subsequent presentationunits, and presentation time information which is indicated by an offsetduration from the decoding time of each presentation unit. In this case,the second and subsequent decoding time information is indicated by theoffset duration from the decoding time of the presentation unit beforeeach of the presentation units, so that the number of bits required forthe encoding time information can be suppressed.

For example, the broadcast signal may include a first packet includingthe transmission media, a second packet including information on thetransmission media, and a third packet including the time informationgenerated by the time information generation unit, and the firstpresentation time and the duration information may be inserted into thesecond packet. In this case, the duration information is inserted intothe second packet including the information on the transmission media,so that it is possible to suppress the delay for performing the processaccording to the decoding time and the presentation time in thereception side down to a low level.

In addition, for example, the broadcast signal may include a firstpacket including the transmission media, a second packet includinginformation on the transmission media, and a third packet including thetime information generated by the time information generation unit, thefirst presentation time may be inserted into the second packet, and theduration information may be inserted into the first packet. In thiscase, the duration information is inserted into the first transportpacket including the transmission media, so that it is possible tosuppress the delay for performing the process according to the decodingtime and the presentation time in the reception side down to a lowlevel.

In this case, for example, the duration information may be inserted intoan extension header of the first packet. In addition, in this case, forexample, when a head of the presentation unit is included, the extensionheader may be installed in the first packet. Therefore, a generatedinformation amount is suppressed, and thus, the bandwidth can be saved.In addition, in this case, for example, the extension header may bealways installed in the first packet, and flag information indicatingwhether or not the head of the presentation unit is included in thefirst packet may be further inserted into the extension header.Therefore, disturbance of the header information amount can besuppressed, and thus, the header process in the reception side can besimplified.

In this manner, in the present technology, the time informationincluding the frequency information of the clock synchronizing with thetime information acquired from the outside is included in the broadcastsignal. Therefore, in the reception side, the same clock (system clock)as that of the transmission side can be generated based on the timeinformation, so that clock synchronization can be implemented.

In addition, in the present technology, the time acquisition informationfor acquiring the decoding time and the presentation time for everypresentation unit of the transmission media obtained based on the timeinformation including the frequency information of the clocksynchronizing with the time information acquired from the outside andsynchronizing with the time information acquired from the outside isincluded in the broadcast signal. Therefore, in the reception side,presentation synchronization can be implemented based on the timeinformation generated based on the time information included in atransmitting signal and the presentation time information for everypresentation unit of the transmission media.

According to another concept of the present technology, there isprovided a reception apparatus including: a reception unit whichreceives a broadcast signal including transmission media, timeacquisition information for acquiring the decoding time and thepresentation time for every presentation unit of the transmission media,and time information including frequency information of a clocksynchronizing with time information acquired from an outside andsynchronizing with the time information acquired from the outside; atime information generation unit which generates a clock based on timeinformation included in the broadcast signal and generates timeinformation synchronizing with the time information by using the clock;a time calculation unit which calculates the decoding time and thepresentation time for every presentation unit of the transmission mediabased on the time acquisition information included in the broadcastsignal; and a process unit which processes the transmission mediaincluded in the broadcast signal for every presentation unit based onthe decoding time and the presentation time calculated by the timecalculation unit and the time information generated by the timeinformation generation unit.

In the present technology, the broadcast signal is received by thereception unit. The broadcast signal includes the transmission media,the time acquisition information for acquiring the decoding time and thepresentation time for every presentation unit of the transmission media,and the time information including the frequency information of theclock synchronizing with the time information acquired from the outsideand synchronizing with the time information acquired from the outside.

For example, the time acquisition information for acquiring the decodingtime and the presentation time for every presentation unit of thetransmission media may include, for every presentation unit groupincluding a predetermined number of the presentation units of thetransmission media, presentation time of the first presentation unit ofthe presentation unit group and duration information for calculating thedecoding time and the presentation time of each presentation unit of thepresentation unit group by referring to the presentation time of thefirst presentation unit. In addition, in this case, the durationinformation may include decoding time information of the presentationunit which is indicated by an offset duration from the presentation timeof the first presentation unit and is firstly transported, informationindicating the duration of each presentation unit, and presentation timeinformation which is indicated by an offset duration from the decodingtime of each presentation unit.

In addition, for example, the broadcast signal may include a firstpacket including the transmission media, a second packet includinginformation on the transmission media, and a third packet including thetime information, and the first presentation time and the durationinformation may be inserted into the second packet. In addition, forexample, the broadcast signal may include a first packet including thetransmission media, a second packet including information on thetransmission media, and a third packet including the time information,the first presentation time may be inserted into the second packet, andthe duration information may be inserted into the first packet.

By the time information generation unit, the clock is generated based onthe time information included in the broadcast signal, and the timeinformation synchronizing with the time information by using the clockis generated. In addition, by the time calculation unit, the decodingtime and the presentation time for every presentation unit of thetransmission media are calculated based on the time acquisitioninformation included in the broadcast signal. In addition, by theprocess unit, the transmission media included in the broadcast signalare processed based on the decoding time and the presentation timecalculated by the time calculation unit and the time informationgenerated by the time information generation unit for every presentationunit.

In this manner, in the present technology, the same clock (system clock)as that of the transmission side and the time information including thefrequency information of the clock are generated based on the timeinformation relating to the time information acquired from the outsideincluded in the broadcast signal. In addition, the transmission mediaare processed for every presentation unit based on the decoding time andthe presentation time for every presentation unit of the transmissionmedia obtained based on the clock, the time information, and the timeacquisition information included in the broadcast signal. Therefore,clock synchronization and presentation synchronization can beimplemented.

Effects of the Invention

According to the present technology, it is possible to well implementclock synchronization and presentation synchronization in a broadcastscheme of performing transportation in an IP scheme. The effectsdisclosed in this specification are exemplary ones and are not limited,and additional effects may be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configurational example of atransmission/reception system as an embodiment.

FIG. 2 is a diagram for explaining clock synchronization andpresentation synchronization in the transmission/reception system.

FIG. 3 is a diagram illustrating an MMT-scheme protocol stack.

FIGS. 4(a) to 4(e) are diagrams illustrating a configurational exampleof an MMT-scheme broadcast stream (broadcast signal).

FIGS. 5(a) and 5(b) are diagrams illustrating a configurational exampleof an MMT packet and an MMT extension header.

FIGS. 6(a) and 6(b) are diagrams illustrating a configurational exampleof an MMTP payload and a DU header.

FIG. 7 is a diagram illustrating an example of correspondence between anMMT file and an MMTP payload.

FIG. 8 is a diagram illustrating a configurational example of a PAmessage and an MP table.

FIG. 9 is a diagram illustrating explanation of main parameters of thePA message.

FIG. 10 is a diagram illustrating explanation of main parameters of theMP table.

FIG. 11 is a diagram illustrating a structural example of an MPU timestamp descriptor.

FIG. 12 is a diagram for explaining a transportation sequence in anMMT-scheme broadcast stream.

FIG. 13 is a diagram illustrating a structural example of an extensionheader where a first form of the offset information is inserted.

FIG. 14 is a diagram illustrating contents of main information in thestructural example of the extension header where the first form of theoffset information is inserted.

FIG. 15 is a diagram illustrating a method of calculating decoding timeDT and presentation time PT according to the first form of the offsetinformation in the reception side.

FIGS. 16(a) and 16(b) are diagrams illustrating a calculation formulafor the decoding time DT and the presentation time PT of eachpresentation unit.

FIG. 17 is a diagram illustrating a structural example of an extensionheader where a second form of the offset information is inserted.

FIG. 18 is a diagram illustrating contents of main information in thestructural example of the extension header where the second form of theoffset information is inserted.

FIG. 19 is a diagram illustrating a method of calculating decoding timeDT and presentation time PT according to the second form of the offsetinformation in the reception side.

FIGS. 20(a) and 20(b) are diagrams illustrating calculation formulas andthe like for the decoding time DT and the presentation time PT of eachpresentation unit.

FIG. 21 is a diagram illustrating a first form of transportationfrequency of an extension header.

FIG. 22 is a diagram illustrating a second form of transportationfrequency of an extension header.

FIG. 23 is a diagram illustrating a structural example of an MPUextended time stamp descriptor.

FIG. 24 is a diagram illustrating a method of calculating decoding timeDT and presentation time PT in the reception side.

FIG. 25 is a diagram illustrating another structural example of the MPUextended time stamp descriptor.

FIG. 26 is a diagram illustrating another structural example of the MPUextended time stamp descriptor.

FIG. 27 is a diagram illustrating a method of calculating decoding timeDT and presentation time PT in the reception side.

FIGS. 28(a) and 28(b) are diagrams illustrating calculation formulas andthe like for the decoding time DT and the presentation time PT of eachpresentation unit.

FIG. 29 is a diagram for explaining delay adjustment for MPT where anMPU extended time stamp descriptor is inserted and AV encoded data.

FIG. 30 is a block diagram illustrating a configurational example of abroadcast transmission system.

FIG. 31 is a block diagram illustrating a configurational example of areceiver.

FIGS. 32(a) to 32(c) are diagrams for explaining an NTP server and aformat of time information supplied by the NTP server.

FIG. 33 is a block diagram illustrating a configurational example of abroadcast transmission system side for explaining clocksynchronization/presentation synchronization method in an MMT scheme.

FIG. 34 is a block diagram illustrating a configurational example of areceiver side for explaining the clock synchronization/presentationsynchronization method in an MMT scheme.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a mode (hereinafter, referred to as an “embodiment”) forcarrying out the invention will be described. The description is made inthe following order.

1. Embodiment

2. Modified Example

1. Embodiment

[Configurational Example of Transmission/Reception System]

FIG. 1 illustrates a configurational example of a transmission/receptionsystem 10 as an embodiment. The transmission/reception system 10 isconfigured with a broadcast transmission system 100 and a receiver 200.

The broadcast transmission system 100 transmits internet protocol (IP)type broadcast signal including transmission media such as a video andan audio. The broadcast transmission system 100 acquires timeinformation from an outside. For example, the time information of an NTPlong format is acquired from an NTP server by a network time protocol(NTP) or from another device by an IEEE 1588 PTP.

The broadcast transmission system 100 generates a clock (system clock)synchronizing with the time information acquired from the outside andtime information including frequency information of the clock. In theembodiment, the frequency of the clock is set to not 27 MHz applied tothe broadcast system in the related art but 2**n. Hz. In addition, inthe embodiment, n=24 is set. However, other integers, for example, anyinteger of 24 to 28 may be used. In this manner, the frequency of theclock is set to 2**n Hz, so that generation of the time informationsynchronizing with the NTP-long-format time information acquired fromthe outside is facilitated, and the generated time information is tocorrespond to the NTP long format.

The broadcast signal includes the transmission media, time acquisitioninformation for acquiring decoding time and presentation time for everypresentation unit of the transmission media obtained based on thegenerated time information, and the generated time information. In theembodiment, the time acquisition information includes, for everypresentation unit group including a predetermined number of thepresentation units of the transmission media, presentation time of thefirst presentation unit of the presentation unit group and offsetinformation for calculating the decoding time and the presentation timeof each presentation unit of the presentation unit group by referring tothe presentation time of the first presentation unit.

The receiver 200 receives the above-described IP-scheme broadcast signalwhich is transmitted from the broadcast transmission system 100. Thereceiver 200 generates the time information including the clock (systemclock) of 2**n Hz synchronizing with the time information included inthe broadcast signal and the frequency information of the clock of 2**nHz based on the time information included in the broadcast signal. Inaddition, the receiver 200 obtains the decoding time and thepresentation time for every presentation unit of the transmission mediabased on the time acquisition information included in the broadcastsignal. The receiver 200 processes the transmission media included inthe broadcast signal based on the obtained decoding time andpresentation time and the generated time information for everypresentation unit.

In the transmission/reception system 10, the broadcast transmissionsystem 100 and the receiver 200 are allowed to have the above-describedconfigurations, so that clock synchronization and presentationsynchronization are implemented similarly to an MPEG2-TS scheme in therelated art.

The clock synchronization and the presentation synchronization in thetransmission/reception system will be described with reference to FIG.2. The transmission system and the reception system correspond to, forexample, the above-described broadcast transmission system 100 and theabove-described receiver 200, respectively. The transmission system isconfigured to include a clock generation unit 11 which generates thesystem clock of 2**n. Hz and a clock unit (time information generationunit) 12 which generates the time information. In addition, thetransmission system is configured to include an encoding process unit13, a packetization/time stamp addition unit 14, and an encode buffer15.

In the encoding process unit 13, the transmission media such as video oraudio are encoded. The packetization/time stamp addition unit 14packetizes the encoded transmission media and adds the presentation timeinformation for every presentation unit of the transmission media basedon the time information generated by the clock unit 12. Next, packets ofthe transmission media are temporarily stored in the encode buffer 15 tobe transmitted at an appropriate timing.

The reception system is configured to include a clock generation unit 21which generates the system clock of 2**n Hz and a clock unit (timeinformation generation unit) 22 which generates the time information. Inaddition, the reception system is configured to include a decode buffer23, a de-packetization/timing adjustment unit 24, and a decoding processunit 25.

The decode buffer 23 temporarily stores the received packets of thetransmission media. The de-packetization/timing adjustment unit 24extracts and de-packetizes the packets of the transmission media storedin the decode buffer 23 by referring to the time information generatedby the clock unit 22 at timing of the added presentation timeinformation. The decoding process unit 25 decodes the transmission mediaobtained through the de-packetization to obtain the transmission mediaof a baseband.

In the transmission/reception system 10 illustrated in FIG. 1, the clocksynchronization and the presentation synchronization are implemented.The clock synchronization/presentation synchronization scheme will bedescribed later in detail. Herein, the clock synchronization basicallydenotes that the frequency of the system clock generated by the clockgeneration unit 11 of the transmission system and the frequency of thesystem clock generated by the clock generation unit 21 of the receptionsystem become the same frequency. However, the frequencies are notnecessarily the same frequency, but it may be favorable that thefrequencies maintain a relationship of integer multiples or the like. Ina case where the clock synchronization is not implemented, during thetime when the reception continues to be performed in the reception side,failure such as occurrence of frame skipping occurs.

The presentation synchronization denotes that the time information ofthe clock unit 12 of the transmission system and the time information ofthe clock unit 22 of the reception system are in accordance with eachother and the presentation time information for every presentation unitof the transmission media is added to the packets of the transmissionmedia. Herein, in a case where the time information of the clock unit 12of the transmission system is in accordance with the time information ofthe clock unit 22 of the reception system, transport delay from thetransmission system to the reception system is considered. In a casewhere the presentation synchronization is not implemented, it cannot beobtained in the reception side that the synchronization of the video andthe audio is taken and appropriate presentation is obtained withoutfailure of the buffer.

Returning to FIG. 1, as described above, the IP-scheme broadcast signalis transmitted from the broadcast transmission system 100 to thereceiver 200. In the embodiment, the IP-scheme broadcast signal istransmitted in an MPEG media transport (MMT) scheme.

FIG. 3 illustrates an MMT-scheme protocol stack. A physical layer (PHY)exists in the lower level. The physical layer includes a modulationscheme, an error correction scheme, and the like. A transport packetlayer of a type length value (TLV) exists on the physical layer. An IPpacket is stacked on the transport packet of the TLV.

In addition, a user datagram protocol (UDP) is stacked on the IP packet.On the other hand, a transport control signal as signaling informationis stacked on the transport packet of the TLV. In addition, an MMTpacket is stacked on the UDP. The payload section of the MMT packetincludes an MMT fragment unit (MFU) including the encoded data of thetransmission media such as video or audio or a signaling messageincluding the information on the transmission media. As illustrated, anetwork time protocol (NTP) packet further including the timeinformation exists on the UDP.

FIGS. 4(a) to 4 (e) illustrate a configurational example of theMMT-scheme broadcast stream (broadcast signal). FIG. 4 (a) illustrates avideo elementary stream (Video ES). The video elementary stream isdivided into chucks with a predetermined size and is disposed in thepayload section of the MFU as illustrated in FIG. 4(b).

As illustrated in FIG. 4(c), an MMT payload header is added to the MFU,so that an MMTP payload is configured. As illustrated in FIG. 4(d), anMMT header is further added to the MMTP payload, so that an MMT packetis configured. In addition, an MMT packet including a signaling messagealso exists in the payload section. As illustrated in FIG. 4(e), an UDPheader, an IP header, and a TLV header are added to the MMT packet, sothat a TLV packet constituting an MMT-scheme broadcast stream isgenerated.

In addition, an NTP packet including time information of the NTP alsoexists in the TLV packet. In addition, although not shown, as the TLVpacket, a TLV packet including an MMT packet of other transmission mediasuch as audio and subtitle also exists. The MMT-scheme broadcast streamincludes a first packet (MMT packet) including transmission media, asecond packet (MMT packet) including signaling information, and a thirdpacket (NTP packet) including time information.

FIG. 5(a) illustrates a configurational example (Syntax) of the MMTpacket. The MMT packet is configured to include the MMT header and theMMT payload. The 1-bit flag information “C” indicates whether or not thefield “packet_counter” exists. The illustrated example illustrates anexample where the “packet_counter” exists. The 2-bit field “FEC”indicates a format of forward error correction (FEC).

The 1-bit flag information “X” indicates whether or not the MMTextension header, that is, the field “header_extension” exists. In theillustrated example, an example where the “header_extension” exists isillustrated. The 1-bit flag information “R” indicates whether or not arandom access point is included, and thus, an I picture is included.

The 6-bit field “type” indicates a type of the MMT packet. For example,“0x00” indicates an MMT packet where a media processing unit (MPU) isincluded in the payload, and “0x02” indicates the MMT packet where asignaling message is included in the payload.

The 16-bit field “packet_id” is an identifier for identifying an assetof video, audio, or the like. The 32-bit field “timestamp” indicates atype stamp for transport, that is, a time when the MMT packet goes outfrom the transmission side. The time is represented in an NTP shortformat. The “packet_sequence_number” indicates a sequence number of theMMT packet having the same “packet_id”. The 32-bit field“packet_counter” indicates the sequence numbers of all the MMT packetsirrespective of the “packet_id”.

When the 1-bit flag information of the above-described “X” is “1”, thefield “header_extension” which is the MMT extension header is disposedafter the 32-bit field “packet_counter”. The field “payload data” andthe field “source_FEC_payload_ID” constituting the MMTP payload existafter that.

FIG. 5(b) illustrates a configurational example (Syntax) of the MMTextension header. The 16-bit field “type” indicates a type of theextension header. The 16-bit field “length” indicates a byte size of thesubsequent extension header. The byte sizes of the extension headers aredifferent according to the types of the extension headers. A body of theextension header is inserted into the field “header_extension_value”.

FIG. 6(a) illustrates a configurational example (Syntax) of the MMTPpayload which is disposed in the field “payload data” of theabove-described MMT packet. This example illustrates the case of the MPUmode where the “type” of the MMT header is “0x00”. The headerinformation exists in the first section. The 16-bit field “length”indicates a byte size of the entire MMTP payload. The 4-bit field “FT”indicates a field type. “0” indicates that the “MPU metadata” areincluded; “1” indicates that the “Movie Fragment metadata” are included;and “2” indicates that the “MFU” is included.

Herein, the MMT fragment unit (MFU) is obtained by subdividing, that is,fragmenting the MPU. For example, in case of a video, the MFU may be setto correspond to one NAL unit. In addition, for example, in case oftransmission on a communication network transport line, the MFU may beconfigured with one MTU size or a plurality of MTU sizes.

In addition, the MPU starts from a random access point (RAP) andincludes one access unit (AU) or a plurality of AUs. More specifically,for example, in some cases, a picture of one group of picture (GOP) mayhave a configuration of one MPU. The MPU is defined according to eachasset. Therefore, an MPU of a video including only the video data isproduced from the asset of the video, and an MPU of an audio includingonly the audio data is produced from the asset of the audio.

The 1-bit flag information “T” indicates whether the timed media aretransported or the non-timed media are transported. “1” indicates thetimed media, and “0” indicates the non-timed media. In the embodiment,the transportation of the timed media is assumed.

The 2-bit field “f_i” indicates whether or not an integer number of thedata units (DU) are inserted in the field “DU payload” and which one ofthe first, intermediate, and last fragments obtained through thefragmentation of the data unit is inserted. “0” indicates that aninteger number of the data units are inserted; “1” indicates that thefirst fragment is inserted; “2” indicates that the intermediate fragmentis inserted; and “3” indicates that the last fragment is inserted.

The 1-bit flag information “A” indicates whether or not a plurality ofthe data units are inserted in the field “DU payload”. “1” indicatesthat the plurality of data unit are inserted, and “0” indicates that theplurality of data units are not inserted. When “f_i” is 1 to 3, the8-bit field “frag_counter” indicates what number of the fragments it is.

The 32-bit field “MPU sequence number” is a number indicating the orderof the MPU and is information identifying the MPU. For example, in acase where one GOP constitutes one MPU, when the “MPU_sequence_number”of a GOP is “i”, the “MPU_sequence_number” of the next GOP becomes“i+1”.

The field “DU_length”, the field “DU_header”, and the field “DU_payload”are disposed after the field “MPU_sequence_number”. The 16-bit field“DU_length” does not exist in case of “A=0” described above, that is, acase where a plurality of data units are not inserted in the field “DUpayload”. In addition, the field “DU_header” does not exist in case of“FT=0/1”, that is, a case where the “MPU metadata” or the “MovieFragment metadata” are included.

FIG. 6(b) illustrates a configurational example (Syntax) of the“DU_header”. This example illustrates a case where “T=1”, that is, acase where the timed media are transported. The 32-bit field“movie_fragment_sequence_number” indicates a sequence number in MFUunit. For example, when an I picture is divided, each divided onebecomes the MFU. The 32-bit field “sample_number” indicates a number inpicture unit, for example, in case of video. The 32-bit field “offset”indicates an offset value (byte value) from the head of the picture, forexample, in case of video.

In the MMT scheme, the transmission media of the video and the like aretransmitted in a contents format based on a fragmented ISO base mediafile format (ISO BMFF). FIG. 7 illustrates an example of correspondencebetween the MMT file and the MMTP payload when the video data of one GOPare transmitted.

The configuration of the MMT file is basically substantially the same asthe configuration of an MP4 file. First, there is a box “ftyp”.Subsequently, there is a box “mmpu” unique to the MMT. Subsequently,there is a box “moon” as metadata of the entire file.

Subsequently, there is a movie fragment. The movie fragment includes abox “moof” in which the control information is inserted and a box “mdat”in which the encoded data of the video are inserted. Herein, since it isassumed that one GOP constitutes one MPU, only one combination of moviefragments exists.

The metadata of each of the boxes “ftyp”, “mmpu”, and “moov” aretransported as “MPU metadata” by one MMT packet. In this case, “FT=0”.The metadata of the box “moot” are transported as “Movie Fragmentmetadata” by one MMT packet. In this case, “FT=1”. The encoded data ofthe video included in the box “mdat” are fragmented into the “MFUs”, andeach MFU is transported by one MMT packet. In this case, “FT=2”.

Next, the MMT package table (MPT) will be described. As described above,in the MMT packet, an MMT packet including signaling messages alsoexists in the payload. As one of the signaling messages, there is apackage access message (PA message) including the MPT. The MPT indicateswhich components (assets) constitute one broadcast service.

FIG. 8 illustrates a configurational example of the package accessmessage (PA message) and the MP table (MPT: MMT Package Table). FIG. 9illustrates explanation of main parameters of the PA message, and FIG.10 illustrates explanation of main parameters of the MP table.

The “message_id” is a fixed value identifying the PA message in varioustypes of the signaling information. The “version” is an 8-bit integervalue indicating the version of the PA message. For example, in a casewhere some parameters constituting the MP table are also updated, +1increment is performed. The “length” is a byte number which is countedjust after the field to indicate the size of the PA message.

The index information of the table disposed in the field of the payloadis disposed in the field “extension”. The same number of the fields“table_id”, the same number of the fields “table_version”, and the samenumber of the fields “table_length” as the number of tables are disposedin the field. The “table_id” is a fixed value identifying the table. The“table_version” indicates the version of the table. The “table_length”indicates the byte number indicating the size of the table.

The MPT and a predetermined number of other tables are disposed in thefield of the payload of the PA message. Hereinafter, a configuration ofthe MPT will be described.

The “table_id” is a fixed value identifying the MP table in varioustypes of the signaling information. The “version” is an 8-bit integervalue indicating the version of the MP table. For example, in a casewhere some parameters constituting the MP table are also updated, +1increment is performed. The “length” is a byte number which is countedjust after the field to indicate the size of the MP table.

The “pack_id” is identification information as the entire packageincluding as the components all the signals and files which aretransported by the broadcast signal. The identification information istext information. The “pack_id_len” indicates the size (byte number) ofthe text information. The field “MPT_descripors” is a storage area ofthe descriptor relating to the entire package. “MPT_dsc_len” indicatesthe size (byte number) of the field.

“num_of_asset” indicates the number of assets (signals, files) ascomponents constituting the package. The following asset loopscorresponding to the aforementioned number are disposed. “asset_id” isthe information (asset ID) uniquely identifying the asset. Theidentification information is text information. “asset_id_len” indicatesthe size (byte number) of the text information. “gen_loc_info” is theinformation indicating the location of the acquisition site of theasset.

The field “asset_descriptors” is a storage area of the descriptorrelating to the asset. “asset_dsc_len” indicates the size (byte number)of the field. As a descriptor stored in the field “asset_descriptors”,there is an MPU time stamp descriptor (MPU_timestamp_descriptor). Thepresentation time of the presentation unit of the head of the MPU isdescribed in the descriptor.

FIG. 11 illustrates a structural example (Syntax) of the MPU time stampdescriptor. The 16-bit field “descriptor_tag” indicates a descriptortype. Herein, the field indicates the MPU time stamp descriptor. The8-bit field “descriptor_length” indicates a length (size) of thedescriptor, and the field indicates the subsequent byte number as thelength of the descriptor.

The same number of combinations of the “MPU_sequence_number” and the“MPU_presentation_time” as the number of MPUs exist. The 32-bit field“MPU_sequence_number” is, as described above, a number indicating theorder of the MPU and is information identifying the MPU. The 64-bitfield “MPU_presentation_time” indicates the presentation time ofpresentation unit of the head of the MPU. For example, in a case whereMPU=GOP, the presentation time indicates the presentation time of thepicture of the head of the GOP.

FIG. 12 illustrates an example of the MMT-scheme transportationsequence. An example of transporting an MPU including video data of oneGOP is illustrated in the figure. First, the MMT packet where thesignaling message including the MPT is included in the payload istransported. The above-described MPU time stamp descriptor is insertedinto the MPT. When the encoding is performed by the encoder, thepresentation time of the picture of the head of the GOP is indexed, andthe presentation time is described in the MPU time stamp descriptor.

After the MMT packet where the signaling message including the MPT isincluded in the payload is transported, the MMT packet where the GOP isincluded in the payload is transported. In this case, the GOP isfragmented to be transmitted in unit of MFU. The MMT payload header isadded before the MFU, so that the MMTP payload is configured. The entireMMTP payload becomes the payload data of the MMT packet.

At this time, although the “MPU metadata” are transported before thedata of the GOP, the “Movie fragment metadata” are transported after thedata of the GOP. The metadata for calculating the decoding time (DT) andthe presentation time (PT) of each picture of the GOP are included inthe “Movie fragment metadata”. Basically, if it is not after the data ofthe GOP are encoded, the information for calculating the DT and the PTof each picture of the GOP cannot be obtained. Therefore, the “Moviefragment metadata” are transported after the data of the GOP.

In a case where the DT and the PT of each picture of the GOP arecalculated by using the “Movie fragment metadata”, in the decoder, thedata of the GOP need to be delayed until the “Movie fragment metadata”are received. Therefore, although the data of the GOP are not delayed inthe transmission side, the data are delayed in the reception side.

[Transportation of DT/PT Information]

In the embodiment, the time acquisition information (DT/PT information)for acquiring the decoding time DT and the presentation time PT forevery presentation unit (sample) of the transmission media is insertedinto the MMT packet where the media processing unit (MPU) is included inthe payload or the MMT packet where the signaling message is included inthe payload to be transported. Therefore, it is possible to suppress thedelay for performing the process according to the decoding time and thepresentation time in the reception side down to a low level.

“Use of MMT Extension Header of MMT Packet”

First, the case of using the MMT extension header (refer to FIGS. 5(a)and 5(b)) of the MMT packet including the MPU (MFU) will be described.In this case, the DT/PT information of each sample (presentation unit)is disposed in the extension header (header_extension) of the MMT packetincluding the sample.

More specifically, the DT/PT information is disposed in the extensionheader including specific type information indicating the DT/PTinformation. In this case, as the DT/PT information, durationinformation for calculating the decoding time and the presentation timeof the presentation unit by referring to the presentation time of thepresentation unit of the head of the MPU described in the MPU time stampdescriptor of the above-described MPT is inserted into the extensionheader.

As the duration information, for example, a first form and a second formare considered as follows. The first form of the duration informationwill be described. The first form of the offset information includesdecoding time information which is indicated by an offset duration fromthe presentation time of the first presentation unit and presentationtime information which is indicated by an offset duration from thedecoding time.

FIG. 13 illustrates a structural example (syntax) of an extension header(header_extension) where the first form of the duration information isinserted. FIG. 14 illustrates contents (semantics) of main informationin the structural example. The 16-bit field “type” indicates theextension header where the DT/PT information is disposed, that is, the“dt_pt_shortcut_extension”.

The 16-bit field “length” indicates the byte size of the extensionheader after that. Herein, the length is a fixed value of “4”. The 1-bitflag information “PU_start_indicator” indicates whether or not the headof the sample (presentation unit) is included in the MMT packet. “1”indicates that the head of the sample is included, and “0” indicatesthat the head of the sample is not included.

The 17-bit field “decoding_time_offset” indicates decoding timeinformation which is indicated by an offset duration from thepresentation time of the first presentation unit. Namely, the fieldrelates to the sample (presentation unit) of the video, the audio, orthe like included in the MMT packet and the decoding time of the sampleis indicated by the offset duration from the “MPU_presentation_time” ofthe MPU including the sample of the MPU time stamp descriptor.

In this case, for example, the field is indicated as a value in unit of1/(2**16) seconds. In this case, the accuracy is about 65 KHz. Inaddition, in this case, since the “decoding_time_offset” has positiveand negative sign bits, for example, when a GOP includes 15 pictures andthe duration is 0.5 seconds, a time width corresponding to two GOPs canbe covered by the 17-bit field “decoding_time_offset”. Therefore, forexample, in a case where, by increasing the accuracy, the field may beindicated as a value in unit of 1/(2**17) seconds, a time widthcorresponding to one GOP can be covered.

The 14-bit field “presentation_time_offset” indicates presentation timeinformation which is indicated by an offset duration from the decodingtime. Namely, the field relates to the sample (presentation unit) of thevideo, the audio, or the like included in the MMT packet and indicatesthe duration of the decoding time and the presentation time of the samesample. In this case, for example, the field is indicated as a value of1/(2**16) seconds.

FIG. 15 illustrates a method of calculating the decoding time DT and thepresentation time PT in the reception side. As illustrated, thepresentation time mpt of the first presentation unit is acquired fromthe field “MPU_presentation_time” of the MPU time stamp descriptorincluded in the MPT as the signaling message. In addition, the decodingtime information dto and the presentation time information pto for everypresentation unit (sample) are acquired from the field“decoding_time_offset” and the field “presentation_time_offset” of theextension header of the MMT packet.

In the reception side, the decoding time DT and the presentation time PTof each presentation unit are calculated based on the acquisitioninformation as illustrated in FIG. 16(b) by using the following Formulas(1) and (2).DT=mpt+dto  (1)PT=DT+pto  (2)

In the reception side, as illustrated in FIG. 16(a), control of decodeand presentation of each presentation unit of the transmission media isperformed according to the time information (NTP) generated based on thetime information transmitted from the transmission side as describedlater and the calculated decoding time DT and the calculatedpresentation time PT.

Next, a second form of the duration information will be described. Thesecond form of the duration information includes decoding timeinformation of the presentation unit which is indicated by an offsetduration from the presentation time of the first presentation unit andis firstly transported, decoding time information which is indicated byan offset duration from the decoding time of the presentation unitbefore each of the second and subsequent presentation units, andpresentation time information which is indicated by an offset durationfrom the decoding time of each presentation unit.

FIG. 17 illustrates a structural example (Syntax) of the extensionheader (header_extension) where the second form of the durationinformation is inserted. FIG. 18 illustrates contents (semantics) ofmain information in the structural example. The 16-bit field “type”indicates the extension header where the DT/PT information is disposed,that is, the “dt_pt_shortcut_extension”.

The 16-bit field “length” indicates the byte size of the extensionheader after that. Herein, the length is a fixed value of “4”. The 1-bitflag information “PU_start_indicator” indicates whether or not the headof the sample (presentation unit) is included in the MMT packet. “1”indicates that the head of the sample is included, and “0” indicatesthat the head of the sample is not included.

The 16-bit field “decoding_time_offset” indicates the decoding timeinformation which is indicated by the offset duration from thepresentation time in relation to the first presentation unit. Inaddition, the field indicates the decoding time information which isindicated by the offset duration from the decoding time in presentationunit before that in relation to each of the second and subsequentpresentation units.

Namely, the field relates to the sample (presentation unit) of thevideo, the audio, or the like included in the MMT packet, and thedecoding time of the sample is indicated by the offset duration from theimmediately-preceding sample. However, only in case of the first sample,the field is indicated by the offset duration from the“MPU_presentation_time” of the MPU including the sample of the MPU timestamp descriptor.

In this case, for example, the field is indicated as a value in unit of1/(2**16) seconds. In this case, the accuracy is about 65 KHz. Inaddition, in this case, since the “decoding_time_offset” has positiveand negative sign bits, for example, when a GOP includes 15 pictures andthe duration is 0.5 seconds, a time width corresponding to one GOP canbe covered by the 16-bit field “decoding_time_offset”. In addition, inthe case of the second form of the offset information, it is estimatedthat the value of the “decoding_time_offset” is not increased as it isunlike the first form of the offset information. Therefore, for example,by increasing the accuracy, the field may be indicated as a value inunit of 1/(2**18) seconds.

The 15-bit field “presentation_time_offset” indicates the presentationtime information indicated by the offset duration from the decodingtime. Namely, the field relates to the sample (presentation unit) of thevideo, the audio, or the like included in the MMT packet and indicatesthe duration of the decoding time and the presentation time of the samesample. In this case, for example, the field indicates a value in unitof 1/(2**16) seconds.

FIG. 19 illustrates a method of calculating the decoding time DT and thepresentation time PT in the reception side. As illustrated, thepresentation time mpt of the first presentation unit is acquired fromthe field “MPU_presentation_time” of the MPU time stamp descriptorincluded in the MPT as the signaling message. In addition, the decodingtime information dto and the presentation time information pto for everypresentation unit (sample) are acquired from the field“decoding_time_offset” and the field “presentation_time_offset” of theextension header of the MMT packet.

In the reception side, the decoding time DT and the presentation time PTof each presentation unit are calculated based on the acquisitioninformation as illustrated in FIG. 20(b) by using the following Formulas(3) and (4).DT=mpt+Σdto  (3)PT=DT+pto  (4)

In the reception side, as illustrated in FIG. 20(a), control of decodeand presentation of each presentation unit of the transmission media isperformed according to the time information (NTP) generated based on thetime information transmitted from the transmission side as describedlater and the calculated decoding time DT and the calculatedpresentation time PT.

“Transportation Frequency of Extension Header”

Next, with respect to the transportation frequency of the extensionheader (header_extension), for example, the following first and secondforms are considered. In the first form, as illustrated in FIG. 21, onlyin a case where the head of the sample (presentation unit) is included,the MMT extension header is installed in the MMT packet. In this case, agenerated information amount is suppressed, and thus, the bandwidth canbe saved.

In the second form, as illustrated in FIG. 22, the MMT extension headeris always installed in the MMT packet. In this case, only in a casewhere the head of the sample (presentation unit) is included,“PU_start_indicator=1” is set. In this case, disturbance of the headerinformation amount can be suppressed, and thus, the header process inthe reception side can be simplified.

As described above, the DT/PT information is inserted into the MMTextension header of the MMT packet to be transported, so that, withoutdelay of the data of the MPU, in response to the reception of the dataof each presentation unit (sample), the decoding time and thepresentation time of the presentation unit can be immediatelycalculated. Therefore, it is possible to suppress the delay forperforming the process according to the decoding time and thepresentation time in the reception side down to a low level.

“Use of MPU Extended Time Stamp Descriptor”

Next, the case of using a newly-defined MPU extended time stampdescriptor (MPU extended timestamp descriptor) will be described. Inthis case, the DT/PT information of each sample (presentation unit) ofthe MPU is disposed in the MPU extended time stamp descriptor.

The MPU extended time stamp descriptor is stored in the field“asset_descriptors” of the MPT (refer to FIG. 8). As the DT/PTinformation of each sample (presentation unit) included in the MPUextended time stamp descriptor, similarly to the description in theabove-described case where the DT/PT information is inserted into theMMT extension header of the MMT packet, first and second forms areconsidered.

Namely, the first form of the duration information includes decodingtime information which is indicated by an offset duration from thepresentation time of the first presentation unit and presentation timeinformation which is indicated by an offset duration from the decodingtime. In addition, the second form of the duration information includesdecoding time information of the presentation unit which is indicated byan offset duration from the presentation time of the first presentationunit and is firstly transported, decoding time information which isindicated by an offset duration from the decoding time of thepresentation unit before each of the second and subsequent presentationunits, and presentation time information which is indicated by an offsetduration from the decoding time of each presentation unit.

FIG. 23 illustrates a structural example (Syntax) of the MPU extendedtime stamp descriptor. The 16-bit field “descriptor_tag” indicates adescriptor type. Herein, the field indicates the MPU extended time stampdescriptor. The 8-bit field “descriptor_length” indicates a length(size) of the descriptor, and the field indicates the subsequent bytenumber as the length of the descriptor.

The same number of the “MPU_sequence_number” and the “number_of_PU” asthe number of MPUs exist. The 32-bit field “MPU_sequence_number” is anumber indicating the order of the MPU and is information identifyingthe MPU. The 16-bit field “number_of_PU” indicates the number of samples(presentation units) included in the MPU. In addition, the same numberof combinations of the 16-bit field “presentation_time_offset” and the16-bit field “decoding_time_offset” as the number of samples(presentation units) exist.

Although the detailed description is omitted, the same decoding timeinformation and presentation time information as those disposed in thefield “decoding_time_offset” and the field “presentation_time_offset” ofthe above-described MMT extension header of the MMT packet (refer toFIGS. 13 and 17) are disposed in the field “decoding_time_offset” andthe field “presentation_time_offset”.

FIG. 24 illustrates a method of calculating the decoding time DT and thepresentation time PT in the reception side. This example illustrates acase where the duration information as the DT/PT information is thesecond form of the duration information.

As illustrated, the presentation time mpt of the first presentation unitis acquired from the field “MPU_presentation_time” of the MPU time stampdescriptor included in the MPT as the signaling message. In addition,the decoding time information dto and the presentation time informationpto of each presentation unit (sample) are acquired from the field“decoding_time_offset” and the field “presentation_time_offset” of theMPU extended time stamp descriptor included in the MPT as the signalingmessage.

In the reception side, the decoding time DT and the presentation time PTof each presentation unit are calculated based on the acquisitioninformation by using the above-described Formulas (3) and (4) (refer toFIG. 20(b)). In the reception side, control of decode and presentationof each presentation unit of the transmission media is performedaccording to the time information (NTP) generated based on the timeinformation transmitted from the transmission side as described laterand the calculated decoding time DT and the calculated presentation timePT (refer to FIG. 20 (a)).

In addition, as the DT/PT information of each sample (presentation unit)included in the MPU extended time stamp descriptor, a third form of theduration information may also be considered which is not described inthe above-described case where the DT/PT information is inserted intothe MMT extension header of the MMT packet. Namely, the third durationinformation includes decoding time information of the presentation unitwhich is indicated by an offset duration from the presentation time ofthe first presentation unit and is firstly transported, informationindicating the duration of each presentation unit, and presentation timeinformation which is indicated by an offset duration from the decodingtime of each presentation unit.

FIGS. 25 and 26 illustrate a structural example (Syntax) of the MPUextended time stamp descriptor. The 16-bit field “descriptor_tag”indicates a descriptor type. Herein, the field indicates the MPUextended time stamp descriptor. The 8-bit field “descriptor_length”indicates a length (size) of the descriptor, and the field indicates thesubsequent byte number as the length of the descriptor.

The 1-bit field “timescale_flg” indicates a flag indicating whether ornot time scale designation is described. In a case where the time scaledesignation is described, the field is set to “1”. In addition, in acase where a pre-defined time scale is used, the field is set to “0”.The 2-bit field “PU_duration_description_type” indicates a descriptiontype of the presentation unit duration. In a case where a pre-definedfixed value is used, the field is set to “0”; in a case where a fixedvalue is designated, the field is set to “1”; and in a case where avalue is designated for every presentation unit, the field is set to“2”.

When “timescale_flg=1”, the 32-bit field “timescale” exists. The fieldis a value indicating a unit of the duration in the descriptor and is avalue such as 90 k or 2**n. The duration obtained by dividing the valueby one second is defined as the unit. In addition, since 32 bits arelarge, it may be considered that the value is indicated according to themode. For example, it may be considered that, as 8 bits, “1” indicates90 k, “2” indicates 2**16, or the like.

When “PU_duration_description_type=1”, the 16-bit field“default_PU_duration” exists. The field indicates the defaultpresentation unit duration which is a fixed value of the presentationunit duration in the effective range of the descriptor based on the timescale. The presentation unit duration is the information indicating theduration of each presentation unit in the“PU_duration_description_type=1”. In addition, in the case of“PU_duration_description_type=0”, since the duration of eachpresentation unit is a defined fixed value, the“PU_duration_description_type=0” itself is the information indicatingthe duration of each presentation unit.

In addition, the same number of the fields “MPU_sequence_number”, thesame number of the fields “SAP_type”, “initial_decoding_time_offset”,and the same number of the fields “number_of_PU” as the number of MPUsexist. The 32-bit field “MPU_sequence_number” is a number indicating theorder of the MPU and is information identifying the MPU.

The 3-bit field “SAP_type” indicates configuration and dependency of theGOP as the MPU. For example, “SAP_type=1” indicates that the GOP startsfrom an I picture and is a closed GOP. In addition, for example,“SAP_type=2” indicates that the GOP starts from a B picture and is aclosed GOP. In addition, for example, “SAP_type=3” indicates that theGOP is an open GOP.

The 16-bit field “initial_decoding_time_offset” is an initial decodingtime offset indicating the decoding time of the presentation unit whichis firstly transported at the offset time from the start point based onthe time scale. The initial decoding time offset is the decoding timeinformation of the presentation unit which is indicated by an offsetduration from the presentation time of the first presentation unit andis firstly transported.

The 8-bit field “number_of_PU” indicates the number of samples(presentation units) included in the MPU. In addition, the same numberof the 16-bit fields “decoding_presentation_time_offset” as the numberof samples exist. The field is a decoding/presentation time offsetindicating the duration from the decoding time to the presentation timeof the same presentation unit based on the time scale. Thedecoding/presentation time offset is the presentation time informationwhich is indicated by an offset duration from the decoding time of eachpresentation unit.

When “PU_duration_description_type=2”, the same number of the 16-bitfields “PU_duration” as the number of samples (presentation units)included in the MPU exist. The field indicates the presentation unitduration for every sample (presentation unit) based on the time scale.The presentation unit duration is the information indicating theduration of each presentation unit in a case where“PU_duration_description_type=2”.

FIG. 27 illustrates a method of calculating the decoding time DT and thepresentation time PT in the reception side. As illustrated, thepresentation time rapt of the first presentation unit is acquired fromthe field “MPU_presentation_time” of the MPU time stamp descriptorincluded in the MPT as the signaling message.

In addition, the decoding time information idto of the presentation unit(sample) which is firstly transported is acquired from the field“initial_decoding_time_offset” of the MPU extended time stamp descriptorincluded in the MPT as the signaling message. In addition, thepresentation time information dpto of each presentation unit (sample) isacquired from the field “decoding_presentation_time_offset” of thedescriptor.

In addition, the information PUd indicating the duration of eachpresentation unit is acquired based on the description information ofthe descriptor. Namely, in a case where“PU_duration_description_type=0”, the information PUd indicating theduration of each presentation unit is defined as a pre-defined fixedvalue. In addition, in a case where “PU_duration_description_type=1”,the information PUd indicating the duration of each presentation unit isacquired as a fixed value from the field “default_PU_duration”. Inaddition, in a case where “PU_duration_description_type=2”, theinformation PUd indicating the duration of each presentation unit isacquired from the field “PU_duration”.

In the reception side, the decoding time DTk and the presentation timePTk of each presentation unit are calculated based on the acquisitioninformation as illustrated in FIG. 28(b) by using the following Formulas(5), (6), and (7).DTk=mpt+((k−1)*PUd−idto)*2^(N) /ts  (5)DTk=mpt+(ΣPUdi−idto)*2^(N) /ts  (6)PTk=DTk+dptok*2^(N) /ts  (7)

The Formula (5) is a formula of calculating the decoding time DTk ofeach presentation unit in a case where“PU_duration_description_type=0/1”. The Formula (6) is a formula ofcalculating the decoding time DTk of each presentation unit in a casewhere “PU_duration_description_type=2”. Herein, the term “ΣPudi” becomes0 in a case where k=1 and becomes the sum from i=1 to k−1 in a casewhere k>1.

Each of the calculation formulas is obtained in the state that the DTkand the PTk are in accordance with the unit, that is, 1/(2**N) secondsof the presentation time mpt of the first presentation unit acquiredfrom the field “MPU_presentation_time” of the MPU time stamp descriptor(refer to FIG. 28(a)). In each formula, in the term “2^(N)/ts”,reduction for allowing the unit indicated by “timescale” to be inaccordance with the unit of the mpt is performed.

In the reception side, control of decode and presentation of eachpresentation unit of the transmission media is performed according tothe time information (NTP) generated based on the time informationtransmitted from the transmission side as described later and thecalculated decoding time DTk and the calculated presentation time PTk asdescribed above (refer to FIG. 28(a)).

Next, a transportation sequence for the MPU extended time stampdescriptor will be described. While the MPU time stamp descriptor isdisposed before the AV data of the MPU, as illustrated in FIG. 29, theMPU extended time stamp descriptor is disposed in the MPT immediately atthe DT/PT determination time before the input of the AV signal to theencoder buffer (Enc Buffer) to be transported as a broadcast stream.

If the delay corresponding to the GOP or more in the buffer exists inthe AV data, since the delay does not exist in the MPU extended timestamp descriptor, the DT/PT information can be set to be in theavailable state in the receiver securely at the time of output from thedecoder buffer (Dec Buffer).

As described above, the DT/PT information is inserted into the MPUextended time stamp descriptor to be transported, so that, without delayof the data of the MPU, in response to the reception of the data of eachpresentation unit (sample), the decoding time and the presentation timeof the presentation unit can be immediately calculated. Therefore, it ispossible to suppress the delay for performing the process according tothe decoding time and the presentation time in the reception side downto a low level.

FIG. 30 illustrates a configurational example of the broadcasttransmission system 100. The broadcast transmission system 100 isconfigured to include an NTP clock generation unit (clock unit) 111, asignal transmission unit 112, a video encoder 113, an audio encoder 114,and an MMT signaling encoding unit 115. In addition, the broadcasttransmission system 100 is configured to include a TLV signalinggeneration unit 116, N IP service multiplexers 117-1 to 117-N, a TLVmultiplexer 118, and a modulation/transmission unit 119.

In the NTP clock generation unit (clock unit) 111, the NTP timeinformation synchronizing with the NTP time information acquired fromthe outside is generated, and the IP packet including the NTP timeinformation is transmitted to the IP service multiplexer 117-1. Thesignal transmission unit 112 is, for example, a studio in a TV stationor a recoding reproducing device such as a VTR and is a system oftransmitting a baseband signal such as a video or an audio astransmission media.

In the video encoder 113, the video signal transmitted from the signaltransmission unit 112 is encoded and is further packetized, and the IPpacket including the MMT packet of the video is transmitted to the IPservice multiplexer 117-1. In the audio encoder 114, the audio signaltransmitted from the signal transmission unit 112 is encoded and isfurther packetized, and the IP packet including the MMT packet of theaudio is transmitted to the IP service multiplexer 117-1.

Herein, in a case where the MMT extension header of the MMT packet isused as described above, the extension header (header_extension)including the time acquisition information (DT/PT information) foracquiring the decoding time (DT) and the presentation time (PT) of thesample (presentation unit) included in the packet is disposed in the MMTpacket of the video or the MMT packet of the audio.

In the MMT signaling encoding unit 115, a signaling message isgenerated, and an IP packet including the MMT packet where the signalingmessage is disposed in the payload section is transmitted to the IPservice multiplexer 117-1. The signaling message includes an MMT packagetable (MPT). The MPU time stamp descriptor (MPU_timestamp_descriptor) isinserted into the MPT. Herein, in the case of using the newly-definedMPU extended time stamp descriptor (MPU_extended_timestamp_descriptor)as described above, the MPU extended time stamp descriptor is furtherinserted into the MPT.

In the IP service multiplexer 117-1, time division multiplexing of theIP packet transmitted from each encoder is performed. At this time, inthe IP service multiplexer 117-1, the UDP header and the TLV header areadded to each IP packet, so that the TLV packet is set. In the IPservice multiplexer 117-1, one channel portion inserted into onetransponder is configured. The IP service multiplexers 117-2 to 117-Nhave the same function as that of the IP service multiplexer 117-1, sothat other channel portions inserted into the one transponder areconfigured.

In the TLV signaling generation unit 116, signaling information isgenerated, and a TLV packet where the signaling information is disposedin the payload section is generated. In the TLV multiplexer 118, the TLVpackets generated by the IP service multiplexers 117-1 to 117-N and theTLV signaling generation unit 116 are multiplexed, so that an MMT-schemebroadcast stream (refer to FIG. 4 (e)) is generated. In themodulation/transmission unit 119, an RF modulation process is performedon the MMT-scheme broadcast stream generated by the TLV multiplexer 118and the resulting stream is transmitted to an RF transport line.

FIG. 31 illustrates a configurational example of the receiver 200. Thereceiver 200 is configured to include a tuner/demodulation unit 201, ademultiplexer 202, an NTP clock reproduction unit (clock unit) 203, anda system control unit 204. In addition, the receiver 200 is configuredto include a video control unit 205, a video decode buffer 206, a videodecoder 207, an audio control unit 208, an audio decode buffer 209, andan audio decoder 210.

In the tuner/demodulation unit 201, an intermediate frequency signal isreceived from an antenna (not shown) and is demodulated, so that theMMT-scheme broadcast stream (refer to FIG. 4(e)) is obtained. In thedemultiplexer 202, a demultiplexing process and a de-packetizationprocess are performed on the broadcast stream, and the NTP timeinformation, the signaling information, the encoded data of the videoand the audio, and the DT/PT information of the video and the audio areextracted.

In the demultiplexer 202, filtering is performed by the MMT-SI filterunit 202 a, so that the signaling information (signaling message) of theMMT is extracted, and the signaling information is transmitted to thesystem control unit 204. In addition, in the demultiplexer 202,filtering is performed by the TLV-SI filter unit 202 b, so that the TLVsignaling information is extracted, and the TLV signaling information istransmitted to the system control unit 204.

The NTP time information extracted by the demultiplexer 202 istransmitted to the NTP clock reproduction unit 203. In the NTP clockreproduction unit 203, the NTP time information synchronizing with theNTP time information is reproduced. The NTP time information reproducedin this manner is transmitted to the video control unit 205 and theaudio control unit 208.

The encoded data of the video extracted by the demultiplexer 202 aretemporarily stored in the video decode buffer 206. In addition, theencoded data of the audio extracted by the demultiplexer 202 aretemporarily stored in the audio decode buffer 209.

In the case of using the MMT extension header of the MMT packet asdescribed above, in the demultiplexer 202, the DT/PT information of thevideo and the audio is extracted from the MMT extension header of theMMT packet of the video and the audio to be transmitted to the videocontrol unit 205 and the audio control unit 208, respectively.

On the other hand, in the case of using the MPU extended time stampdescriptor as described above, in the system control unit 204, the DT/PTinformation of the video and the audio is extracted from the MPUextended time stamp descriptor of the video and the audio of the MPT(refer to FIG. 23, FIG. 25, or FIG. 26) to be transmitted to the videocontrol unit 205 and the audio control unit 208, respectively.

In addition, in the system control unit 204, the presentation time ofthe first sample (presentation unit) of the MPU of the video and theaudio is extracted from the MPU time stamp descriptor of the video andthe audio of the MPT (refer to FIG. 11) to be transmitted to the videocontrol unit 205 and the audio control unit 208, respectively.

In the video control unit 205, the decoding time DT and the presentationtime PT of each sample (presentation unit) are calculated based on thepresentation time of the first sample (presentation unit) of the MPU andthe DT/PT information of each sample (presentation unit) of the MPU(refer to the above-described Formulas (1) and (2), Formulas (3) and(4), or Formulas (5), (6), and (7)).

In the video control unit 205, the video decoder 207 is allowed toperform instruction of the decoding and the presentation on the encodedvideo of each sample (presentation unit) stored in the video decodebuffer 206. In this case, in the video control unit 205, the instructionis performed at the timing of the decoding time DT and the presentationtime PT obtained as described above by referring to the NTP timeinformation supplied from the NTP clock reproduction unit 203.

In the video decoder 207, a decoding process is performed on the encodedvideo of each sample (presentation unit) stored in the video decodebuffer 206 based on the instruction from the video control unit 205.Therefore, the video of each sample (presentation unit) is sequentiallyoutput from the video decoder 207 at the timing of the presentation timePT.

In addition, in the audio control unit 208, the decoding time DT and thepresentation time PT of each sample (presentation unit) are calculatedbased on the presentation time of the first sample (presentation unit)of the MPU and the DT/PT information of each sample (presentation unit)of the MPU (refer to the above-described Formulas (1) and (2), Formulas(3) and (4), or Formulas (5), (6), and (7)).

In the audio control unit 208, the audio decoder 210 is allowed toperform instruction of the decoding and the presentation on the encodedaudio of each sample (presentation unit) stored in the audio decodebuffer 209. In this case, in the audio control unit 208, the instructionis performed at the timing of the decoding time DT and the presentationtime PT obtained as described above by referring to the NTP timeinformation supplied from the NTP clock reproduction unit 203.

In the audio decoder 210, a decoding process is performed on the encodedaudio of each sample (presentation unit) stored in the audio decodebuffer 209 based on the instruction from the audio control unit 208.Therefore, the audio of each sample (presentation unit) is sequentiallyoutput from the audio decoder 210 at the timing of the presentation timePT.

Now, the network time protocol (NTP) will be described. The NTP is aprotocol regulated as a standard of the Internet by the internationaltelecommunication union (ITU). A client such as a personal computer or asmartphone accesses the NTP server according to the NTP protocol, sothat the time information is obtained.

As illustrated in FIG. 32(a), layers (Stratum) exist for the NTPservers, and the lower the number is, the higher the accuracy is. Forexample, the NTP server of the layer 1 (Stratum 1) is immediatelyassociated with an atomic clock, and the error of the time informationis less than 1 μs. The time information supplied by the NTP server isexpressed by the number of seconds accumulated from Jan. 1, 1900 (UTC:Coordinated Universal Time).

FIG. 32(b) illustrates a format (NTP time stamp long format) of the timeinformation supplied by the NTP server. The time information is of a64-bit format, the upper 32 bits indicate the number of accumulatedseconds of the UTC, and the lower 32 bits indicate sub-second. FIG.32(c) illustrates a format (NTP time stamp short format) of the timeinformation supplied by the NTP server. The time information is of a32-bit format, the upper 16 bits indicate the number of accumulatedseconds of the UTC, and the lower 16 bits indicate sub-second.

In a case where the client such as a personal computer or a smartphoneaccesses the NTP sever according to the NTP protocol and the timeinformation is acquired, it is unclear which layer of the NTP server isaccessed. Therefore, a plurality of the NTP servers are synchronouslyaccessed and an average value is taken, so that the variation issuppressed and more accurate time information is obtained.

FIGS. 33 and 34 illustrate clock synchronization/presentationsynchronization method in the MMT scheme. FIG. 33 illustrates aconfigurational example of the broadcast transmission system 100 side.FIG. 34 illustrates a configurational example of the receiver 200 side.

First, a configurational example of the broadcast transmission system100 side will be described with reference to FIG. 33. The broadcasttransmission system 100 is configured to include an NTP/IP interface 131and 32-bit registers 132 a and 132 b. In addition, the broadcasttransmission system 100 is configured to include a voltage controlledoscillator 133 which generates a clock (system clock) of 2**24 Hz, an8-bit counter 134 a, a 16-bit counter 134 b, and a 32-bit counter 134 cwhich constitute the clock unit, and a comparator 135. In addition, thebroadcast transmission system 100 is configured to include apacketization unit 136, a video encoding process unit 137, apacketization unit 138, an encode buffer 139, a video synchronizationcontrol unit 140, an MMT signaling encoding unit 141, and a multiplexer142.

For example, the NTP/IP interface 131 accesses the NTP server (notshown) via the Internet in a predetermined time interval, so that the64-bit-format time information (refer to FIG. 32 (b)) is acquired. Inthe 32-bit registers 132 a and 132 b, the 64-bit-format time informationacquired by the NTP/IP interface 131 is stored. The bit data of theupper 32 bits are stored in the 32-bit register 132 a, and the bit dataof the lower 32 bits are stored in the 32-bit register 132 b. Thecontents stored in the 32-bit registers 132 a and 132 b are updatedevery time when the 64-bit-format time information is acquired by theNTP/IP interface 131.

Herein, in a case where the frequency of acquisition of the timeinformation is sufficiently high, the above-described configuration isfavorable. However, in a case where the frequency is low, it may beconsidered that the registers 132 a and 132 b are continuously operatedas the counter automatically indicating the time so that the clock ofthe NTP server is reproduced. Herein, at the time when the outputs ofthe register 132 b indicating the lower 32 bits of the acquired timeinformation become all zeros, the outputs of the registers 132 aindicating the upper 32 bits of the time information are set to theinitial values of the 32-bit counter 134 c, and the 16-bit counter 134 band the 8-bit counter 134 a are set to all zeros. The setting operationis limited to one time when the broadcast transmission system 100 isactivated.

In the voltage controlled oscillator 133, the clock of 2**24 Hz (systemclock) is generated. In the 8-bit counter 134 a, the clock of 2**24 Hzoutput from the voltage controlled oscillator 133 is counted. In the16-bit counter 134 b, the carry output of the 8-bit counter 134 a iscounted. Namely, in the embodiment, the 8-bit counter 134 a and the16-bit counter 134 b constitute a 24-bit counter.

In the 32-bit counter 134 c, the clock of 1 Hz which is the carry outputof the 16-bit counter 134 b is counted, so that the bit output of the 32bits which is highly accurate time information (regenerated UTC) can beobtained. The 56-bit bit output of the 8-bit counter 134 a, the 16-bitcounter 134 b, and the 32-bit counter 134 c becomes the system timeclock (STC) as the time information by the operation of the counter fromthe initial value.

In the comparator 135, at the timing of updating the contents stored inthe 32-bit registers 132 a and 132 b, the above-described 56-bit systemtime clock is latched and is compared with the contents stored in theregisters, that is, the time information (excluding the lower 8 bits)acquired from the NTP server. Next, a comparison error signal issupplied as a control signal from the comparator 135 to the voltagecontrolled oscillator 133.

The voltage controlled oscillator 133, the counters 134 a, 134 b, and134 c, and the comparator 135 constitute a Phase Locked Loop (PLL)circuit. Therefore, in the voltage controlled oscillator 133, a clock(system clock) of 2**24 Hz synchronizing with the 64-bit-format timeinformation acquired from the NTP server is generated. In addition, inthe counters 134 a, 134 b, and 134 c, a 56-bit time informationincluding the frequency information of the clock of 2**24 Hz andsynchronizing with the 64-bit-format time information acquired from theNTP server is generated.

The 56-bit time information is supplied to the packetization unit 136.In the packetization unit 136, 8 bits of all zeros are added to thelower levels of the 56-bit time information to obtain a 64-bit-formattime information (refer to FIG. 28(b)). In the packetization unit 136,an IP packet including the NTP clock reference (NTP_CR:NTPClockReference) having the frequency information of the clock of2**24 Hz is generated based on the 64-bit time information.

In the video encoding process unit 137, the video (video data) isencoded in synchronization with the clock of 2**24 Hz obtained by thevoltage controlled oscillator 133. In this case, the clock of 2**24 Hzis appropriately multiplied or divided to be converted into a desiredfrequency to be used. In the packetization unit 138, an elementarystream of the encoded video is divided into chunks with a predeterminedsize, and an MMT packet where each chunk is included in the payloadsection is generated. The MMT packet is transmitted through the encodebuffer 139 to the multiplexer 142.

In the MMT signaling encoding unit 141, a signaling message isgenerated, and an IP packet including the MMT packet where the signalingmessage is disposed in the payload section is transmitted to themultiplexer 142.

The 56-bit time information obtained by the counters 134 a, 134 b, and134 c is supplied to the video synchronization control unit 140. In thevideo synchronization control unit 140, the presentation time (PT) ofeach picture for every GOP of the video encoded by the video encodingprocess unit 138 is obtained based on the encode timing of the picture(sample=presentation unit) of the head. The presentation time mpt issupplied to the MMT signaling generation unit 141.

In the MMT signaling encoding unit 141, for every GOP of the videoencoded by the video encoding process unit 138, the MPU time stampdescriptor (MPU_timestamp_descriptor) including the presentation timempt of the picture is generated, and the signaling message including theMMT package table (MPT) where the descriptor is inserted is generated.

In addition, in the video synchronization control unit 140, for everyGOP of the video encoded by the video encoding process unit 138, theabove-described DT/PT information (time acquisition information foracquiring the decoding time DT and the presentation time PT) isgenerated based on the encode timing of each picture.

In the case of using the MMT extension header of the MMT packet asdescribed above, the DT/PT information generated by the videosynchronization control unit 140 is supplied to the packetization unit138. In the packetization unit 138, the MMT extension header(header_extension) including the DT/PT information is disposed in theMMT packet of the video.

In addition, in the case of using the MPU extended time stamp descriptor(MPU_extended_timestamp_descriptor) as described above, the DT/PTinformation generated by the video synchronization control unit 140 issupplied to the MMT signaling encoding unit 141. In the MMT signalingencoding unit 141, for every GOP of the video encoded by the videoencoding process unit 138, the MPU extended time stamp descriptorincluding the DT/PT information of each picture is generated, and thesignaling message including the MMT package table (MPT) where thedescriptor is inserted is generated.

As described above, the IP packet including the NTP clock reference, theMMT packet including the encoded video, and the MMT packet including thesignaling message are supplied to the multiplexer 142. In addition,although not shown, the MMT packet including the encoded audio and thelike is generated similarly to the MMT packet including the encodedvideo, and the MMT packet is supplied to the multiplexer 142. In themultiplexer 142, further necessary headers are added to each packet, sothat the MMT-scheme broadcast stream is generated. The MMT-schemebroadcast stream is transmitted as the broadcast signal.

Next, a configurational example of the receiver 200 side will bedescribed with reference to FIG. 34. The receiver 200 is configured toinclude a demultiplexer 231, a voltage controlled oscillator 232 whichgenerates a clock (system clock) of 2**24 Hz, an 8-bit counter 233 a, a16-bit counter 233 b, and a 32-bit counter 233 c which constitute aclock unit, and a comparator 234. In addition, the receiver 200 isconfigured to include an MMT signaling decoding unit 235, a videosynchronization control unit 236, a de-packetization unit 237, a decodebuffer 238, and a video decoding process unit 239. Herein, the voltagecontrolled oscillator 232 generating the system clock does notnecessarily have the same frequency as that of the transmission system,and for example, even in the case of 2**22 Hz, 2**n (n is an integer)may be used.

The MMT-scheme broadcast stream as the received broadcast signal issupplied to the demultiplexer 231. In the demultiplexer 231, the NTP_CRis extracted from the IP packet including the NTP clock reference(NTP_CR). During the tuning or during the power supplying, the upper 56bits of the first received 64-bit NTP_CR are set to initial values inthe 56-bit counter configured with the counter 233 a, the counter 233 b,and the counter 233 c, and the subsequently received NTP_CRs aresupplied to the comparator 234.

The voltage controlled oscillator 232, the counters 233 a, 233 b, and233 c, and the comparator 234 constitute a phase locked loop (PLL)circuit. Therefore, in the voltage controlled oscillator 232, the clockof 2**24 Hz synchronizing with the NTP_CR is generated. The frequency ofthe clock of 2**24 Hz becomes equal to the frequency of the clockgenerated by the voltage controlled oscillator 133 of the broadcasttransmission system 100 described above, so that the clocksynchronization is implemented.

In addition, in the counters 233 a, 233 b, and 233 c, a system timeclock synchronizing with the NTP_CR is generated. The system time clockis in accordance with the system time clock generated by the counters134 a, 134 b, and 134 c of the broadcast transmission system 100described above. Therefore, as described above, the information(presentation time mpt and DT/PT information) for acquiring the decodingtime DT and the presentation time PT for every presentation unit of thevideo and the audio is inserted into the MT-scheme broadcast stream, sothat the presentation synchronization is implemented.

The signaling message extracted by the demultiplexer 231 is supplied tothe MMT signaling decoding unit 235. In the MMT signaling decoding unit235, the presentation time mpt of the picture for every GOP of the videois extracted from the MPU time stamp descriptor(MPU_timestamp_descriptor) included in the MMT package table (MPT). Thepresentation time mpt is supplied to the video synchronization controlunit 236.

In addition, in the case of using the MPU extended time stamp descriptor(MPU_extended_timestamp_descriptor) as described above, in the MMTsignaling decoding unit 235, the DT/PT information of each picture forevery GOP of the video is extracted from the MPU extended time stampdescriptor included in the MMT package table (MPT). The DT/PTinformation is supplied to the video synchronization control unit 236.

The MMT packet including the encoded video extracted by thedemultiplexer 231 is supplied to the de-packetization unit 237 to bede-packetized. The encoded video obtained by the de-packetization unit237 is temporarily stored in the decode buffer 238.

In addition, in the case of using the MMT extension header of the MMTpacket as described above, in the de-packetization unit 237, the DT/PTinformation of each picture for every GOP of the video is extracted fromthe MMT extension header (header_extension) included in the MMT packet.The DT/PT information is supplied to the video synchronization controlunit 236.

The system time clock generated by the counters 233 a, 233 b, and 233 cis supplied to the video synchronization control unit 236. In this case,all the 56 bits are not necessarily supplied, but only the number ofbits corresponding to the accuracy of the decoding time DT and thepresentation time PT calculated by the video synchronization controlunit 236 may be supplied.

For example, in a case where the accuracy of the decoding time (DT) andthe presentation time (PT) calculated by the video synchronizationcontrol unit 236 is 1/2**16 seconds (about 15 μs), only the (32+16)-bitoutput of the 32-bit counter 233 c and the 16-bit counter 233 b issufficient. In addition, in the case of the higher accuracy, forexample, 1/2**18 seconds (3.8 μs), the bit output of the 8-bit counter233 a is also needed.

In the video synchronization control unit 236, the decoding time DT andthe presentation time PT of each picture for every GOP of the video arecalculated based on the presentation time mpt and the DT/PT information(refer to the above-described Formulas (1) and (2), Formulas (3) and(4), or Formulas (5), (6), and (7)). In the video synchronizationcontrol unit 236, the video decoding process unit 239 is allowed toperform instruction of the decoding and the presentation on the encodedvideo of each picture stored in the decode buffer 238. In this case, inthe video synchronization control unit 236, the instruction is performedat the timing of the decoding time DT and the presentation time PTobtained as described above by referring to the system time clockgenerated by the counters 233 a, 233 b, and 233 c.

In the video decoding process unit 239, a decoding process is performedon the encoded video of each picture stored in the decode buffer 238based on the instruction from the video synchronization control unit236. Therefore, the video of each picture is sequentially output fromthe video decoding process unit 239 at the timing of the presentationtime PT. In addition, although not shown, in the demultiplexer 231, theMMT packet including the encoded audio is also extracted and isprocessed similarly to the case of the above-described video to obtainthe audio data of the baseband, so that the audio is output.

As described above, in the transmission/reception system 10 illustratedin FIG. 1, the time information (NTP_CR) including the frequencyinformation of the clock synchronizing with the time informationacquired from the outside is included in the MMT-scheme broadcaststream. Therefore, in the reception side, the same clock (system clock)as that of the transmission side can be generated based on the timeinformation, so that the clock synchronization can be implemented.

In this case, the frequency of the clock is set to 2**n Hz (for example,n=24 to 28), so that generation of the time information synchronizingwith the NTP-long-format time information acquired from the outside isfacilitated, and the generated time information can be allowed tocorrespond to the NTP long format.

In addition, in the transmission/reception system 10 illustrated in FIG.1, the information (presentation time mpt, DT/PT information) foracquiring the decoding time DT and the presentation time PT for everypresentation unit of the video and the audio obtained based on timeinformation (system time clock) synchronizing with the time informationacquired from the outside is inserted into the MMT-scheme broadcaststream. Therefore, the presentation synchronization can be implementedbased on the information and the time information (system time clock).

In addition, in the transmission/reception system 10 illustrated in FIG.1, the MMT extension header of the MMT packet or a newly-defined MPUextended time stamp descriptor is used for transportation of the DT/PTinformation for acquiring the decoding time DT and the presentation timePT of each sample (presentation unit). Therefore, it is possible tosuppress the delay for performing the process according to the decodingtime and the presentation time in the reception side down to a lowlevel.

2. Modified Example

In the above-described embodiment, the example of treating theMMT-scheme broadcast stream is illustrated. Although detaileddescription is omitted, the present technology can be applied to even acase where the same broadcast stream is taken to be used.

In addition, the present technology may take the configuration asfollows.

(1) A transmission apparatus including:

a clock generation unit which generates a clock synchronizing with timeinformation acquired from an outside;

a time information generation unit which generates time informationincluding frequency information of the clock generated by the clockgeneration unit and synchronizing with the time information acquiredfrom the outside; and

a transmission unit which transmits a broadcast signal includingtransmission media, time acquisition information for acquiring decodingtime and presentation time for every presentation unit of thetransmission media obtained based on the time information generated bythe time information generation unit, and the time information generatedby the time information generation unit.

(2) The transmission apparatus according to (1),

wherein the time acquisition information includes,

for every presentation unit group including a predetermined number ofthe presentation units of the transmission media,

presentation time of the first presentation unit of the presentationunit group and

duration information for calculating the decoding time and thepresentation time of each presentation unit of the presentation unitgroup by referring to the presentation time of the first presentationunit.

(3) The transmission apparatus according to (2),

wherein the duration information includes

decoding time information of the presentation unit which is indicated byan offset duration from the presentation time of the first presentationunit and is firstly transported, information indicating the duration ofeach presentation unit, and presentation time information which isindicated by an offset duration from the decoding time of eachpresentation unit.

(4) The transmission apparatus according to (2),

wherein the duration information includes

decoding time information which is indicated by an offset duration fromthe presentation time of the first presentation unit and presentationtime information which is indicated by an offset duration from thedecoding time for each of the presentation units.

(5) The transmission apparatus according to (2),

wherein the duration information includes

decoding time information of the presentation unit which is indicated byan offset duration from the presentation time of the first presentationunit and is firstly transported, decoding time information which isindicated by an offset duration from the decoding time of thepresentation unit before each of the second and subsequent presentationunits, and presentation time information which is indicated by an offsetduration from the decoding time of each presentation unit.

(6) The transmission apparatus according to any one of (2) to (4),

wherein the broadcast signal includes a first packet including thetransmission media, a second packet including information on thetransmission media, and a third packet including the time informationgenerated by the time information generation unit, and

the first presentation time and the duration information are insertedinto the second packet.

(7) The transmission apparatus according to any one of (2) to (4),

wherein the broadcast signal includes a first packet including thetransmission media, a second packet including information on thetransmission media, and a third packet including the time informationgenerated by the time information generation unit,

the first presentation time is inserted into the second packet, and

the duration information is inserted into the first packet.

(8) The transmission apparatus according to (7), wherein the durationinformation is inserted into an extension header of the first packet.

(9) The transmission apparatus according to (8),

wherein, when a head of the presentation unit is included, the extensionheader is installed in the first packet.

(10) The transmission apparatus according to (8),

wherein the extension header is always installed in the first packet,and flag information indicating whether or not the head of thepresentation unit is included in the first packet is further insertedinto the extension header.

(11) The transmission apparatus according to any one of (1) to (10),

wherein a frequency of the clock generated by the clock generation unitis 2**n Hz.

(12) A transmitting method including:

a clock generating step of generating a clock synchronizing with timeinformation acquired from an outside;

a time information generating step of generating time informationincluding frequency information of the clock generated in the clockgenerating step and synchronizing with the time information acquiredfrom the outside; and

a transmitting step of transmitting a broadcast signal includingtransmission media, time information for acquiring decoding time andpresentation time for every presentation unit of the transmission mediaobtained based on the time information generated in the time informationgenerating step, and the time information generated in the timeinformation generating step.

(13) A reception apparatus including:

a reception unit which receives a broadcast signal includingtransmission media, time acquisition information for acquiring thedecoding time and the presentation time for every presentation unit ofthe transmission media, and time information including frequencyinformation of a clock synchronizing with time information acquired froman outside and synchronizing with the time information acquired from theoutside;

a time information generation unit which generates a clock based on timeinformation included in the broadcast signal and generates timeinformation synchronizing with the time information by using the clock;

a time calculation unit which calculates the decoding time and thepresentation time for every presentation unit of the transmission mediabased on the time acquisition information included in the broadcastsignal; and

a process unit which processes the transmission media included in thebroadcast signal for every presentation unit based on the decoding timeand the presentation time calculated by the time calculation unit andthe time information generated by the time information generation unit.

(14) The reception apparatus according to (13),

wherein the time acquisition information for acquiring the decoding timeand the presentation time for every presentation unit of thetransmission media includes,

for every presentation unit group including a predetermined number ofthe presentation units of the transmission media,

presentation time of the first presentation unit of the presentationunit group and

duration information for calculating the decoding time and thepresentation time of each presentation unit of the presentation unitgroup by referring to the presentation time of the first presentationunit.

(15) The reception apparatus according to (14),

wherein the duration information includes

decoding time information of the presentation unit which is indicated byan offset duration from the presentation time of the first presentationunit and is firstly transported, information indicating the duration ofeach presentation unit, and presentation time information which isindicated by an offset duration from the decoding time of eachpresentation unit.

(16) The reception apparatus according to (14) or (15),

wherein the broadcast signal includes a first packet including thetransmission media, a second packet including information on thetransmission media, and a third packet including the time information,and

the first presentation time and the duration information are insertedinto the second packet.

(17) The reception apparatus according to (14) or (15),

wherein the broadcast signal includes a first packet including thetransmission media, a second packet including information on thetransmission media, and a third packet including the time information,

the first presentation time is inserted into the second packet, and

the duration information is inserted into the first packet.

(18) A reception method including:

a receiving step of receiving a broadcast signal including transmissionmedia, time acquisition information for acquiring the decoding time andthe presentation time for every presentation unit of the transmissionmedia, and time information including frequency information of a clocksynchronizing with time information acquired from an outside andsynchronizing with the time information acquired from the outside;

a time information generating step of generating a clock based on timeinformation included in the broadcast signal and generating timeinformation synchronizing with the time information by using the clock;

a time calculating step of calculating the decoding time and thepresentation time for every presentation unit of the transmission mediabased on the time acquisition information included in the broadcastsignal; and

a processing step of processing the transmission media included in thebroadcast signal for every presentation unit based on the decoding timeand the presentation time calculated in the time calculating step andthe time information generated in the time information generating step.

(19) A transmission apparatus including:

a clock generation unit which generates a clock of 2**n Hz synchronizingwith time information acquired from an outside;

a time information generation unit which generates time informationincluding frequency information of the clock of 2**n Hz generated by theclock generation unit and synchronizing with the time informationacquired from the outside; and

a transmission unit which transmits a broadcast signal includingtransmission media, time information for acquiring decoding time andpresentation time for every presentation unit of the transmission mediaobtained based on the time information generated by the time informationgeneration unit, and the time information generated by the timeinformation generation unit.

(20) The transmission apparatus according to (19), wherein the n is anyone of integers of 24 to 28.

The main features of the present technology are to use the MMT extensionheader of the MMT packet or a newly-defined MPU extended time stampdescriptor for transportation of the DT/PT information for acquiring thedecoding time DT and the presentation time PT of each sample(presentation unit), so that it is possible to suppress a delay forperforming a process according to the decoding time and the presentationtime in a reception side down to a low level (refer to FIGS. 15, 19, 24,and 27). In addition, a main feature of the present technology is that afrequency of a system clock is set to 2**n Hz (for example, n=24 to 28),so that generation of time information synchronizing withNTP-long-format time information acquired from an outside isfacilitated, and the generated time information can be allowed tocorrespond to an NTP long format (refer to FIG. 33).

REFERENCE SIGNS LIST

-   10 Transmission/reception system-   100 Broadcast transmission system-   111 NTP clock generation unit-   112 Signal transmission unit-   113 Video encoder-   114 Audio encoder-   115 MMT signaling encoding unit-   116 TLV signaling generation unit-   117-1 to 117-N IP service multiplexer-   118 TLV multiplexer-   119 Modulation/transmission unit-   131 NTP/IP interface-   132 a, 132 b 32-bit register-   133 Voltage controlled oscillator-   134 a 8-bit counter-   134 b 16-bit counter-   134 c 32-bit counter-   135 Comparator-   136 Packetization unit-   137 Video encoding process unit-   138 Packetization unit-   139 Encode buffer-   140 Video synchronization control unit-   141 MMT signaling encoding unit-   142 Multiplexer-   200 Receiver-   201 Tuner/demodulation unit-   202 Demultiplexer-   202 a MMT-SI filter unit-   202 b TLV-SI filter unit-   203 NTP clock reproduction unit-   204 System control unit-   205 Video control unit-   206 Video decode buffer-   207 Video decoder-   208 Audio control unit-   209 Audio decode buffer-   210 Audio decoder-   231 Demultiplexer-   232 Voltage controlled oscillator-   233 a 8-bit counter-   233 b 16-bit counter-   233 c 32-bit counter-   234 Comparator-   235 MMT signaling decoding unit-   236 Video synchronization control unit-   237 De-packetization unit-   238 Decode buffer-   239 Video decoding process unit

The invention claimed is:
 1. A transmission apparatus comprising: a timeacquisition information generation unit which generates time acquisitioninformation for acquiring decoding time and presentation time for everypresentation unit of transmission media; and a transmission unit whichtransmits a broadcast signal including the transmission media and thetime acquisition information, wherein the time acquisition informationincludes, for every presentation unit group including a predeterminednumber of presentation units of the transmission media, presentationtime of a first presentation unit of the presentation unit group,duration information for calculating the decoding time and thepresentation time of each presentation unit of the presentation unitgroup by referring to the presentation time of the first presentationunit, the broadcast signal includes a first packet including thetransmission media and a second packet including information on thetransmission media, the presentation time of the first presentation unitand the duration information are inserted into the second packet, andthe duration information includes decoding time information of thepresentation unit which is indicated by an offset duration from thepresentation time of the first presentation unit and is firstlytransported, information indicating the duration of each presentationunit, and presentation time information which is indicated by an offsetduration from the decoding time of each presentation unit.
 2. Atransmitting method comprising: a time acquisition informationgenerating step of generating time acquisition information for acquiringdecoding time and presentation time for every presentation unit oftransmission media; and a transmitting step of transmitting a broadcastsignal including the transmission media and the time acquisitioninformation, wherein the time acquisition information includes, forevery presentation unit group including a predetermined number ofpresentation units of the transmission media, presentation time of afirst presentation unit of the presentation unit group and durationinformation for calculating the decoding time and the presentation timeof each presentation unit of the presentation unit group by referring tothe presentation time of the first presentation unit, the broadcastsignal includes a first packet including the transmission media and asecond packet including information on the transmission media, thepresentation time of the first presentation unit and the durationinformation are inserted into the second packet, and the durationinformation includes decoding time information of the presentation unitwhich is indicated by an offset duration from the presentation time ofthe first presentation unit and is firstly transported, informationindicating the duration of each presentation unit, and presentation timeinformation which is indicated by an offset duration from the decodingtime of each presentation unit.
 3. A reception apparatus comprising areception unit which receives a broadcast signal including transmissionmedia and time acquisition information for acquiring decoding time andpresentation time for every presentation unit of the transmission media,wherein the time acquisition information includes, for everypresentation unit group including a predetermined number of presentationunits of the transmission media, presentation time of a firstpresentation unit of the presentation unit group and durationinformation for calculating the decoding time and the presentation timeof each presentation unit of the presentation unit group by referring tothe presentation time of the first presentation unit, the broadcastsignal includes a first packet including the transmission media and asecond packet including information on the transmission media, thepresentation time of the first presentation unit and the durationinformation are inserted into the second packet, the durationinformation includes decoding time information of the presentation unitwhich is indicated by an offset duration from the presentation time ofthe first presentation unit and is firstly transported, informationindicating the duration of each presentation unit, and presentation timeinformation which is indicated by an offset duration from the decodingtime of each presentation unit, and the reception apparatus furtherincludes: a time calculation unit which calculates the decoding time andthe presentation time for every presentation unit of the transmissionmedia based on the time acquisition information included in thebroadcast signal; and a process unit which processes the transmissionmedia included in the broadcast signal for every presentation unit basedon the decoding time and the presentation time calculated by the timecalculation unit.
 4. A reception method comprising: a receiving step ofreceiving a broadcast signal including transmission media and timeacquisition information for acquiring decoding time and presentationtime for every presentation unit of the transmission media, wherein thetime acquisition information includes, for every presentation unit groupincluding a predetermined number of presentation units of thetransmission media, presentation time of a first presentation unit ofthe presentation unit group and duration information for calculating thedecoding time and the presentation time of each presentation unit of thepresentation unit group by referring to the presentation time of thefirst presentation unit, the broadcast signal includes a first packetincluding the transmission media and a second packet includinginformation on the transmission media, the presentation time of thefirst presentation unit and the duration information are inserted intothe second packet, the duration information includes decoding timeinformation of the presentation unit which is indicated by an offsetduration from the presentation time of the first presentation unit andis firstly transported, information indicating the duration of eachpresentation unit, and presentation time information which is indicatedby an offset duration from the decoding time of each presentation unit,and the reception method further includes: a time calculating step ofcalculating the decoding time and the presentation time for everypresentation unit of the transmission media based on the timeacquisition information included in the broadcast signal; and aprocessing step of processing the transmission media included in thebroadcast signal for every presentation unit based on the decoding timeand the presentation time calculated in the time calculating step.